Method for making waterproof paper board



Nov. 12, 1929.` l E. BACHE 1,735,030

METHOD FOR MAKING' WATERPROOF PAPER BOARD Fi1e d Nov. N8. 1926 gwumtoz 4.frs

,aan

EDMUND BAGHE, 0F ST. PAUL, MDINESOTA, ASSIGNOR TO WALDORF PAPER PRODUCTS COMPANY, OF ST. PAUL, MINNESOTA, A CORPORATION OF MINNESOTA METHOD FOB MAKING WATERPROOF PAPER IBOABl) Application med November 8, 1926. Serial No. 146,963.

interior plies of the board. To adapt the,

product for use in constructing cartons land v other paper board containers, 1t is necessary that the outer surfaces be porous or free from waterproofing materialother than the usual sizing. The waterproofing material has been applied either by mixing it with the stock supplied to one of the cylinders of a cylinder v4as paper machine orl by spraying or otherwise spreading it upon an internal web or ply of the sheet during the passage ofthe web between successive cylinders.' Unimpregnated webs or layers are then formed upon the waterproof layer during the passage of the web over the succeeding cylinders of themachine, and the sheet is finally dried. Experience has taught that where a waterproofing agent in emulsiied form, such as an emulsion of the soap type, is allowed to remain in the sheet, this agent spreads to the surfaces, resulting in a stainin or dyeing of the exterior by the emulsion. uch surface stains on the sheet render it unsuited for use in the construction of food containers and also interfere with printing upon the surface and destroy the attractive appearancexof the board.

I t is the object of this invention to avoid such surface stains and to improve thewaterproo qualities ot the board by concentrating the waterproof material in the interior thereof.

Brieilystated, my invention consists in applying an emulsion of a waterproof material, such as asphalt to the wet paper web andthen breaking down the emulsion, Vso that the asphalt particles coalesce in a natural state upon an interior web, after-which the web continues through the machine and reoeves :further layers of paper stock and is inally passed through the dryer, where the heat spreads the asphalt particles, forming a continuous interior film. A suitable asphalt emulsion ma be made from a natural asphalt blonde Vwith petroleum asphalt and emulsied by a soap type of emulsier.

to apply a suita About three percent of sodium oleate and about forty per cent of water will form the desired emulsion with such asphalt. A suit-- D able electrolyte for breaking down the emulsion may consist of a ve per cent solution of sulphuric acid, sprayed, or otherwise spread upon the emulsion.

The invention will be best understoodby reference to the accompanying drawings, in which one form of my improved means are shown attached to a cylinder` paper machine of common type, the machine being illustrated diagrammatically. As here shown, the machine has six cylinders, indicated by the numerals 1 to 6 inclusive, adapted to form the paper web from stock supplied to vats 7. A continuous blanket or felt 8 for supporting the paper web is passed over the upper periphery of the cylinders l to 6, inclusive, successively, and is held in contact therewith by suitable couch rolls 9. As will be readily understood, the cylinders 1 to 6 apply s uccessively layers of stock upon theielt 8. Between two of the cylinders, such as the cylinders 2 and 3, I rovide a roller 10, adapted ble liquid waterproof material or emulsion thereof to the paper web formed by the cylinders 1 and 2. This roller 10 extends across the web in contact with the bottom surface thereof, and is revolved within a small tank 11, adapted to be supplied with the'waterproof material or emulsion through a pi e 12. Thus, a layer or film of waterproo material is applied to the web as it passes over the roller 10.

and is slotted or otherwise perforated along its upper periphery so as to spray the electrolyte u on the surface of the sheet previously supphed with the emulsion. The e'ect of ,the spraying of the emulsion with an electrolyte of ositive nature is to break down the emu sion and cause the waterproof material to coalesce in its natural state upon the pa er web. Now the web passes over the cylindpers .3, 4, 5, and 6 successively. where further layers of stock are applied. Finally, the

paper web is carried on in the usual manner between felt blankets to the dryers and, after drying, is delivered as a ysheet Vhaving a waterproof core and relatively pervious or porous surface plies. The heat of thefdryers liqueiies the asphalt in the interior layers and causes it to spread in al continuous'film. In the finished sheet, the asphalt is concentrated in the interior plies and is 'in' its natural gummy state. It does not spread to the surfaces of the sheet during the drying as is the case when the more liquid orl chemically active emulsions and particularly those of the soap type are dried in the sheet.

It will be obvious that other methods of breaking down the emulsion may comprise impressing an electrostatic charge of positivev nature upon the sheet, instead of applying the electrolyte spray above described.. Further, anysuitable salt which will form an electrolyte of positive nature in an aqueous solution could also be used. T husaluminum sulphate, ferrie, chlorideorcalcium chloride are suitable for forming the electrolyte spray in an aqueous solution. Nor is the .present invention limited to the above describedmethod of applying the emulsion to the sheet.

An important feature of this process is its adaptability for use with emulsions containing an emulsifying agent of a chemically partially ydecomposed or oxidized upon vthe application of the heat ofthe dryers. Thus,

the rectifying agent in no way detracts from the quality of the product, and it is even difficult to detect its presence in the sheet.

`Having described my invention what I claim as new and desire to protect by Letters Patent is:

1. The method of making waterproof paper board which consists in iirst forming an unimpregnated portion of the board, then applying to the interior surface of said por- .tion an emulsified waterproof material without an admixture of fibrous stock, then breaking down the emulsion Without the application of heat to deposit Y the waterproof material upon the bres in substantially natural state and subsequently ydrying the sheet.

2. The method of' making waterproof 'paper board, which consists in applying to vparticles tol coalesce upon the fibresV and finally drying the sheet by the application of heat whereby the asphalt is spread in a suband the emulsifying agent is at least"l partially decomposed. v 3. The method of rendering paper board substantially impervious to moisture, which consists in first applying to a previously formed web an emulsion of a Waterproof material of fusible nature, then breaking down said emulsion to cause said material to coalesce upon the fibres without the application of heat. and finally spreading the coalesced waterproof material by the application of heat to the sheet to thereby form a substantially continuous layer of said material.

4. The method of rendering paper substantially impervious to moisture which consists in first forming a pervious portion of the sheet, then applying to an exposed surface of said portion an emulsified waterproof material of a fusible nature, then breaking down the emulsion without theapplication of heat to thereby cause said waterproof material to coalesce upon the fibres, then covering said waterproof material with pervious layers of stock and subsequently drying the sheet by the application of heat sufficient toliquefy and spread said material. f

. 5. The method of rendering paper boardl substantially impervious to moisture, which consists in applying to a, previousl formed web emulsified Waterproof materia containingan emulsifying agent of chemically. active type and without an admixture of fiber, then applying upon the exposed film of emulsion Eths forned a dilute acid adapted to break' down the emulsion and subsequently drying the sheet by the application' of heat suflicient to at least partially decompose said emulsifying agen 6. The method of making waterproof paper board which consists in first forming an nimpregnated portion of the board, then applying to the interior surface of said portion an emulsied waterproof material containing an emulsifying agent of chemically active nature, then breaking down the emulsion to deposit the waterproof material upon the fibres in substantially naturalstate and subsequently drying the sheet by the applicalos y tion of heat sufficient to at least partially decompose said emulsifyin agent.v

Inv testimony whereo I have hereunto signed my name to this specification.

l EDMUND BACHE.

stantially continuous llm within the. sheet, 

